Electric induction furnace



Oct. 13, 1931. D. wlLLcox 1,827,274

ELECTRIC vvINDUGTION FURNACE Filed Aug. 13, 1928 2 Sheets-Sheet l Oct.13, 1931. D. wlLLcoX ELECTRIC INDUCTION FURNACE Filed Aug. l5, 1928 2Sheets-Sheet 2 y Patented Oct. 13, 1931 y UNITED STATES PATENT OFFICEDUDLEY wxnLoOx, or LAWEENOEVILLE, NEWJEESEY, AssrGNon. 'ro aux ELECTRO-'.rHEEiincl conrona'non, or AJA-x rmx, NEW JERSEY, A oOErOEA'rIoN or NEWJERSEY- ELEcrnIc nmucrrON FURNAUE Application led August 13, 1988,Serial No. 299,158, and in Great Britain September 8, 1927.

My invention relates to the cooling of wind seen 1n Figure 9.

ings for electric induction furnaces.

One purpose of my invention is to utilize the conductivity of copper, tocarry the heat away from a section so that water-cooling can be eifectedby water located in aprotected position.

'A further purpose is to form the currentcarrying part of an inductor ofsolid material close to the furnace and to locate the A further purpose1s to attach cooling elements to"a furnace coil at intervals only aboutthe circumference, relying upon these eleiuents to cool by heatconductivity those por- 2d tions of thefcoil lying between.

Further purposes will appear in the speci- {ication and in the claims.

I have preferred to illustrate my invention by a few forms only amongthe many irr which it may appear, selecting forms which :1re practical,eliicient and reliable and which at the same time well illustrate theprinciples of my invention.

Figure 1 is a topplan view showing one,

embodiment of my invention.

Figure 2 is a section of Figure 1 taken upon line 2 2.

Figure 3 is a view correspondin to Figure 1 showing the invention applieat inter.

vals about the furnace coil.

Figure 4 is a side elevation ture seen in Figure 3.

vof ther struc- Figure 5 is a section of Figure 3 taken upon line 5 5. Al

Figure 6 is a top plan view of a furnace in which coil supportsinterfere with the placing of the cooling elements.

Figure 7 is aside elevation of the structure seen in Figure 6.-

Figure 8 is a section upon line 8-8 of Figure 6.

`Figure 9 is a top plan view of a further form.

Figure 9afis a fragmentary top plan view showing a slight modificationof Figure 9.

Figure 10 is aside "elevation of the form Figure 11 isa section ofFigure 9 taken upon line 11-11.

Figure 12 is a fragmentary section similar to Figure 11, but showing amodilication.

In the drawings similar numerals indicate like parts.

My invention is intended to safeguardl application of water cooling tothe coils of electric furnaces and, though applicable most convenientlyand to the greatest benefit to inductor coils for furnaces of theso-called coreless type (lacking interthreading of the coils bytransformer or crucible lron) is suited also for use with windings ofso-called core type furnaces.

By illustrating the coreless type only it is not intended to suggestthat the invention is' useful in this type alone.

Existing windings of furnace inductor coils are made of tubing or ofsolid strips or straps of copper. The tubing is cooled by water passingthrough the tubing. Onesample of water cooled coils is Ato be seen inNorthrup Patent, No. 1,328,336. I

When the inductor is made of solid metal it is necessary to cool thecoil by ablastof air or other means to take the place of thewater'coolingin the hollow ytubular form.

My invention contemplates cooling an otherwise solid coil by watercooled means llocated outside of the coil where the wate'rcarryingmembers are protected against flow of molten metal leaking from thefurnace. These water cooling members may be attached to the coils, butordinarily used to be attached at intervals only along the length of thecoils. Insteadof direct connection to the coils it is ordinarilysuicient to attach the members to the coils at intervals along the coillengths by heat-conducting tabs.

The points of attachment may be located at different points along thelengths of the coilsor at different points about the circumference orboth. In the case of larger coils it is desirable to put several tabs oneach turn.

Though the invention is valuable for small furnaces lits paramount valueas a safeguard example, which will completely fill the space between theturns instead of the small insulating pieces at intervals about the coilnow required with air cooled coils in order to give greater room forpenetration of cooling air between the turns.

This makes it possible to carry more turns per axial inch of coil lengththan previously and to obtain a greater number of ampere turns about agiven mass or charge of material to be heated than could otherwise besecured.

The additional safety of the present invention as compared with theusual form of water cooled coil made of conducting tubing through, whicha stream of water is passed will be clear `fromthe fact that moltenmetal leaking through the insulation of a furnace' using a tubularcurrent-carrying inductor coil may melt the inside of one or more of theconducting turns of the coil.- This would not only allow the moltenmetal to engage the water, but this would take place at a point on theinside of the coil 'where the rev sulting steam or vapor cannot escape,with the possibility of an explosion which would blow molten metal outof the furnace. An interior line of discharge of the water from the coilalso throws the water toward the charge increasing the danger. Thepresent invention keeps the cooling liquid well away from the moltenmetal, discharges the cooling lituid outwardly and utilizes the coil asa shie d and guard against flow of molten metal and water toward eachother.

In Figures 1 and 2 the inductor 15 is wound from a copper strip ofrectangularcross-section. Every few turns the strip inductor isconnected by sheet copper tabs 16 with copper tubing 17 brazed to thetabs. The tubes'are connected together by sections 18 of rubber hose.Inlet and outlet for water supply and discharge are shown at 19 and 20.The surplus heat from the coil is conducted to the' cooling tubesthrough the tabs and is carried away through the water.

In Figures 3, 4 and 5the tabs and water- 'cooled tubes connected. withthe inductor water directly through the blocksand the pass 18and-nipples 22. These passages with their Walls in the blocks are viewedas in effect tubes but the larger masses of these block tabs, theirlarger number and more general distribution and the better Contact ofthewater with the tabs from the standpoint of heat conduction makes thisform avery much beter cooling system than that in Figures 1 an 2.

In each of these forms shown in Figures 1-5 each turn of the inductorforms a single .strip of copper.

In Figures 6 to 12, however, each inductor turn comprises a plurality ofstrips 15 electrically in parallel, greatly increasing the conductivityof the turn. In all of these ligures heat insulation within the coil isshown at 23, electrical insulation between the coil and the heatinsulation is shown at 24 and insulation between the conductors of eachturn to reduce eddy currents and between the turns is seen at 25. InFigures 6, 7 and 8 non-metallic coil supports are shown at 26.

Figures 9, 10 and 11 correspond in all of these parts with Figures 6, 7and 8 except for the fact that laminated magnetic return circuits forthe ma etic flux of the coil are shown at 27 instea of the coil supports26.

The water cooling of Figure 6 1s secured b attened copper tubing 28flat-wound a ut the turns and brazed or soldered to the turns betweenthe supports or at any other suitable interval as at 29 and outwardlyextended to pass about the non-metallic supports between these points asat 30.

In Figure 9a where the laminated return circuits are spaced enough f romthe coil to permit the water-cooling tube to continue along the outsideof the strips the tubing 28 is in continuous contact with the solid stricomprising the electrically conducting coll.

Connectlons with inlet and outlet tubing 19 and 20 are made throughnipples 31 en,- gaging with the tubing for example, at a point where itis not attened.

In addition to the difference of Figures 9, 10 and `11 from 6, 7 and 8,in that magnetic return laminated material is shown at 27 instead of thecoil supports, these latter figures differ also from Figures 6, 7 and 8in that the flattened Vhollow conductors 28 are not continuousabout thecoil but are interrupted by the insertion of connecting tubing 1-8 toprovide for transitionv about the laminated magnetic return circuit.

In both of the forms shown in Figures 6 to 11 the same hollowwatercooling conductor is connected to cool a number of conductors inparallel, making up a complete turn of the inductor and engaging thecontour of these conductors at intervalsor following the contour withsuch continuity about the ages are connected in seriesvby rubber tubing/circumference as may be required to cool the inductor eectively. l i

In all of the forms the liquid conduit is on the outside where it is`protected from flow of molten metal not only by the turns of theinductor itself but by any electrical insulation or other filling whichmay be desired, permitting com lete sealing of the melt from thewater-carrylng, tube by a wall formed by the current-carry'g part of theinductor and the insulation wit 1n it and between its conductors. d

The selection of the form of cooling and the number of places aboutthecircumference of the coil at which the cooling is applied depend.ofcourse upon the needs of t e individual installatlons. Myillustrations for l this reason have been suggested merely as ways inwhich my invention may be carried out so as to place the cooling tubingon the outside where leakage of water from it will least affect thecharge and furnace and where the tubing is best protected from flow `of-metal from the charge. The cooling system is not confined so aspossibly to result in a serious explosion if it be voverheated.

For large furnaces of the high frequency induction t pe holdin forexample, ve tons of stee it wouldgbe desirable to have 4the furnacelcoilmade of a plurality of layers of edgewise wound copper strips of strapsa proximately as shown in Figures 8 and 11. ery thin insulatingmaterial, such as mica, should be used between the individual turns toprevent setting up of eddy currents and it is desirable to'have thecopper .or other conductor as close as possible to the furnace 1. In acooling system for furnace coils, an inductor and water-cooled tabs atintervals onthe outside of the inductor adapted to cool the inductor andprotected from. the furnace charge bythe body of the inductor.

2. In un electric furnace an inductor coil of edge-wound materialtabsconnected with the ind uctor at intervals and extending outwardly. fromthe inductor and water-cooled connections with the tabs for cooling theinductor through the tabs.

3. In an electric furnace, an inductor coil, water-cooled connectionsoutside of the coil at intervals and Vtubing between the connections tosupply the water cooling progresslvely about the inductor length.

4. In an electric furnace, a vertical inductor coil, magneticmateriali-spaced at intervals about the inductor to form a magneticreturn path, water-cooled tubing thermally connected with the inductor.to cool it at intervals between the ma etic circuit parts, andconnections about t e magnetic clrcuit to su ply water to the tubing.

5. n' an electric furnace, an inductor and water-cooled device forcooling the inductor, thermally connected with the inductor at intervalsabout the inductor length and se arated from the inductor, andconnections etween the devices to supply waterto them.

6. In'- an electric furnace, a` solid metal primary winding, soli'dmetal tabs connected to the primary at intervals along the length of theprimary and water-cooled tubing in heat-transfering connection with thetabs.

DUDLEY WILLCOX.

charge. Not all of the conductors of a turn need be in thermal contactwith the cooling element. In Figure 12 alternate layers o the strapconductors extend further away from the furnace charge than the layersofA conductors between them, so that they cooling water is still furtherremoved from the hot metal for the sake of safety. In such aconstruction good heat-conducting .contact is desirable between theintervening those engaging the tube.

The use of a water cooled tube continuous ly enga the outer e of thecoil, as s own in 1 re 9a, woul be more efectiva nd less like y to givetrouble than the other orms.

In view of my invention and disclosure variations andmodiiications tomeet individual whim or particular need will doubtless become'evident toothers skilled in the art, to obtain part or all of .the'benets of myinvention without oop v the structure shown,and I, therefore, c aimallsuch in so far as theyfall within the reasonable spirit and scope of minvention. 1

Having thus descri my invention, what I claim as new and desire toobtain by Letters Patent 1s: l p

strips and

